1. Field of the Invention
The present invention relates to a thyristor and more particularly to a thyristor with an auxiliary emitter.
2. The Prior Art
The thyristor described in Patalong application U.S. Ser. No. 199,520 employs an auxiliary emitter with an auxiliary emitter electrode for the purpose of providing internal trigger amplification. The stability of the thyristor, i.e., its security against unintentional trigger operations caused by large voltages applied in the forward conducting direction, is increased by means of at least one disconnectible circuit path designed as an MIS structure which connects the auxiliary emitter by a low resistance path to the base layer adjacent thereto. In addition, the emitter of the thyristor is provided with a plurality of fixed emitter short-circuits. The MIS structure has a control terminal to which a control voltage pulse is supplied which shuts off the current path for the duration of the trigger ooperation.
Thyristors with n- or p-emitters and which are provided with controllable emitter short-circuits are known from the U.S. Pat. No. 3,243,669 (for example, FIG. 9) and from the German Patent No. 23 25 917. In these thrysitors, disconnectible current paths are provided in the form of MIS structures which are turned on only for the purpose of rapid quenching of the thyristors. The quenching current paths are formed with a first semiconductor region of a first conductivity type at the edge of the n(p)-emitter, with a second semiconductor region of the same conductivity type inserted into the base layer adjacent in the n(p)-emitter at a distance therefrom, and a subregion of the base layer lying between the semiconductor regions and exhibiting a second conductivity type and covered by an insulated gate. The German patent referred to above also describes the engaging of current paths during the occurrence of an ignition pulse in order to prevent an ignition.
None of the previously known thyristor designs, however, provide an arrangement in which current paths allocated to an auxiliary emitter are switched on before the ignition of a thyristor in order to stabilize a thyristor, and are switched off during the trigger operation.